1. Field of the Invention
This invention relates to well tools having a normally projecting pawl for engaging surfaces in a well. The pawl is retracted once it performs its intended function. Redressing of the pawl is accomplished much more easily than has heretofore been possible for a retracted pawl.
2. The Prior Art
Several common well tools have a normally projecting pawl for engaging a surface in a well. The engagement of the pawl with the well surface may locate the well tool with respect to the well surface (see U.S. Pat. Nos. 4,002,203; 3,965,979; 3,876,001; 3,827,490; 3,610,336; and 2,571,934), orient the well tool with respect to the well tubing (see U.S. Pat. Nos. 4,002,203; 3,965,979; 3,876,001; 3,837,398; 3,827,490; and 3,610,336) and/or actuate the well tool (see U.S. Pat. Nos. 4,002,203; 3,965,979; 3,876,001; 3,827,490; and 3,610,336).
For positive engagement with the well surface, the pawl preferably presents a square shoulder, e.g., a shoulder that forms substantially a right angle with respect to the direction of movement of the well tool through the well. (Such shoulders are disclosed in U.S. Pat. Nos. 4,002,203; 3,965,979; 3,876,001; 3,827,490; and 3,610,336).
Once the pawl has engaged the proper well surface and performed its desired function, the pawl is preferably retracted prior to further movement of the well tool through the well. An unnecessarily projecting pawl is particularly undesirable for through-the-flow-line (T.F.L.) pump down well equipment. A projecting pawl has a relatively small surface area compared with the surface area of other components of the well tool. Therefore, during movement of the well tool through the well, particularly if the well is highly deviated or if the flow line extends substantially horizontally along the sea bed, the pawl will be engaged by the tubing and will wear. The resulting wear necessitates that the pawl be replaced frequently. Additionally, through-the-flow-line (T.F.L.) pump down equipment is comprised of short tool sections interconnected by articulating joints. When forces are applied to a tool train formed of such equipment, the tool train may buckle about the articulating joints. Projecting pawls may engage a surface in the well and cause its tool section to hang up in the well. Therefore, to prevent wear on the pawl and to reduce the likelihood that the tool will hang up as it moves through the well tubing, the pawl is retracted after it has performed its useful function. However, once the well tool has returned to the surface, the pawl must be redressed prior to rerunning the tool in the well. If redressing is complicated or takes too much time, work crew expense increases and the number of operations that may be performed using the well tool within a given time interval decreases.
Present well tools having a projecting pawl either do not have a properly retractable pawl or have a complicated manner of redressing the pawl.
The projecting pawls disclosed in U.S. Pat. Nos. 3,965,979 and 3,876,001 are not maintained in a fully retracted position. Therefore, they will wear and will possibly engage a well shoulder resulting in tool hang-up if they were utilized on through-the-flow-line (T.F.L.) pump down equipment.
The projecting pawls disclosed in U.S. Pat. Nos. 4,002,203; 3,827,490; and 3,610,336 are resiliently urged towards a position projecting beyond the tool body even after the pawl has been rendered ineffective for providing a positive stop. Therefore the pawl will wear as the tool moves through the well, and the pawl may engage a well shoulder and hang up the tool. Additionally, there is no disclosed manner of maintaining the rotational alignment between the pawl and the tool body once the pawl is rendered partially inoperative. Therefore, redressing potentially could be time consuming.
The well tool disclosed in U.S. Pat. No. 2,571,934 does not include a positive means for moving the pawl to a fully retracted position. If the disclosed shearable member, which holds the pawl in its projecting position, does not shear with a clean fracture, galling may occur between the shearable member and the tool components. Such galling would inhibit free movement of the pawl towards its fully retractable position. Additionally, if the well is highly deviated or includes a pump down loop, the pawl possibly will not be maintained in a fully retracted position during passage of the tool through the highly deviated portion of the well or through the well loop.
Resilient means are generally relied upon to urge the pawl towards its operative, projecting position. Preferably, such resilient means provide a substantially constant, non-binding force on the pawl regardless of the extent of retraction or projection of the pawl. The forces provided by a leaf spring possibly vary depending upon the pawl position. Utilizing a coil spring behind the pawl as disclosed in U.S. Pat. Nos. 3,965,979 and 3,876,001 does not permit full retraction of the pawl once it is rendered inoperative. The ball and coil spring arrangement disclosed in U.S. Pat. No. 3,837,398 binds so that free movement of the pawl is inhibited.